In wireless communication systems, a radio access network generally comprises one or more access nodes (such as a base station) which communicate on radio channels over a radio or air interface with plural wireless terminals. In some technologies such a wireless terminal is also called a User Equipment (UE). A group known as the 3rd Generation Partnership Project (“3GPP”) has undertaken to define globally applicable technical specifications and technical reports for present and future generation wireless communication systems. The 3GPP Long Term Evolution (“LTE”) and 3GPP LTE Advanced (LTE-A) are projects to improve an earlier Universal Mobile Telecommunications System (“UMTS”) mobile phone or device standard in a manner to cope with future requirements.
Work has started in the International Telecommunications Union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) 5G systems, e.g., fifth generation systems. Within the scope of 3GPP, a new study item (SID) “Study on New Radio Access Technology” has been approved. The timeline and the study situations of NR development are summarized in RP-161596, “Revision of SI: Study on New Radio Access Technology”, 3GPP TSG RAN Meeting #73, New Orleans, Sep. 19-22, 2016. In order to fulfill 5G requirements, changes with regard to 4G LTE system have been proposed for study, such as higher frequency spectrum usage (e.g., 6 GHz, 40 GHz or up to 100 GHz), scalable numerology (e.g., different subcarrier spacing (SCS), 3.75 KHz, 7.5 KHz, 15 KHz (current LTE), 30 KHz . . . possibly 480 KHz), beam based initial access (one traditional cell may contain multiple beams due to the particular beamforming adopted).
In an LTE system, hierarchical synchronization signals, i.e., primary synchronization sequences (PSS) and secondary synchronization sequences (SSS) provide coarse time/frequency synchronization, physical layer cell ID (PCI) identification, subframe timing identification, frame structure type (FDD or TDD) differentiation and cyclic prefix (CP) overhead identification. On the other hand, in the legacy LTE system, a physical broadcast channel (PBCH) provides further information, such as system frame number (SFN) and essential system information so that a wireless terminal (e., UE) can obtain information to access the network.
In LTE system, three PSS sequences provide identification of cell ID (0-2); and SSS sequences provide identification of cell ID group (0-167). Therefore, in all 168*3=504 PCI IDs are supported in the LTE system.
It is anticipated that in the next generation new radio (NR) technology, a cell corresponds one or multiple transmission and reception point (TRPs). This means multiple TRPs can share the same NR cell ID, or each transmission and reception point (TRP) may have its own identifier. Further, the transmission of one TRP can be in the form of single beam or multiple beams. Each of the beams may also possibly have its own identifier. FIG. 14 provides a simple example depiction of a relationship between cell, transmission and reception point (TRP), and beam.
It has been agreed in RAN1 #86bis meeting (See, e.g., 3GPP RAN1 #86bis Chairman's Notes) that:                PSS, SSS and/or PBCH can be transmitted within a ‘SS block’                    Multiplexing other signals are not precluded within a ‘SS block’                        One or multiple ‘SS block(s)’ compose an ‘SS burst’        One or multiple ‘SS burst(s)’ compose a ‘SS burst set’                    The Number of SS bursts within a SS burst set is finite.                        From RAN1 specification perspective, NR air interface defines at least one periodicity of SS burst set (Note: Interval of SS burst can be the same as interval of SS burst set in some cases, e.g., single beam operation)FIG. 1 is an example NR SS block structure according to the RAN1 #86bis meeting. In FIG. 2, “synchronization signal bursts series” represents a “SS burst set”. Additional detailed examples are illustrated in R1-1610522, “WF on the unified structure of DL sync signal”, Intel Corporation, NTT DOCOMO, ZTE, ZTE Microelectronics, ETRI, InterDigital, Lisbon, Portugal, 10-14 Oct. 2016.        
Thus, as indicated above, one or multiple SS block(s) compose an SS burst. One or multiple SS burst(s) further composes a SS burst set where the number of SS bursts within a SS burst set is finite. If it is always the case that one SS burst composes an SS burst set, then there is actually no meaning for defining SS burst, or a definition of SS burst is not necessary. From physical layer specification perspective, at least one periodicity of SS burst set is supported. From the UE perspective, SS burst set transmission is periodic and a UE may assume that a given SS block is repeated with a SS burst set periodicity, which means SS block may have different periodicity than the SS burst set.
According to 3GPP RAN1 #87 Chairman's Notes, it has been further agreed in [4] that, from the UE perspective, SS burst set transmission is periodic, and that at least for initial cell selection, the UE may assume a default periodicity of SS burst set transmission for a given carrier frequency
In LTE, PSS/SSS and PBCH have different periodicity due to different detection performance requirements and different methods to combat channel distortion (PBCH has channel coding and repetition to combat channel distortion, while PSS/SSS does not).
For initial cell selection for a new radio (NR) cell, the UEs assume a default SS burst set periodicity per frequency carrier. In a cellular network, the CONNECTED mode UEs might need to do the measurement (RSRP/RSRQ or their equivalent measurement) to perform handover; while the IDLE mode UEs might need to do the measurement to perform cell selection/reselection. In legacy LTE systems, the SS transmission has only one fixed periodicity (5 ms) throughout the network; while in NR systems, one value from a set of SS burst set periodicities might be configured to the UE.
For CONNECTED and IDLE mode UEs (UEs already camping on NR cells), New Radio supports network indication of SS burst set periodicity and information to derive measurement timing/duration (e.g., time window for NR-SS detection). The network provides one SS burst set periodicity information per frequency carrier to the UE and information to derive measurement timing/duration if possible. In case that one SS burst set periodicity and one information regarding timing/duration are indicated, the UE assumes the periodicity and timing/duration for all cells on the same carrier. If the network does not provide an indication of SS burst set, periodicity and information to derive measurement timing/duration the UE should assume 5 ms as the SS burst set periodicity. New Radio supports a set of SS burst set periodicity values for adaptation and network indication.
For the purpose of detecting a non-standalone NR cell (e.g., NR carrier not supporting initial access, or other reasons the UE will not camp on the NR cell), NR-SS can still be used at least for cell identification and initial synchronization, and CONNECTED mode RRM measurements. Similarly as for CONNECTED and IDLE mode UEs, NR supports network indication of SS burst set periodicity and information to derive measurement timing/duration (e.g., time window for NR-SS detection). The network provides one SS burst set periodicity information per frequency carrier to UE and information to derive measurement timing/duration if possible. In case that one SS burst set periodicity and one information regarding timing/duration are indicated, the UE assumes the periodicity and timing/duration for all cells on the same carrier. New Radio supports a set of SS burst set periodicity values for adaptation and network indication.
In light of the foregoing, various technical questions and challenges remain. For example:                (1) What if the UE's assumption on SS burst set periodicity is different from the network configuration, especially when there is an update on SS burst set periodicity in the cell to change the periodicity from default value to other value?        (2) What if more than one periodicity/timing/duration can be configured to UE and UE has no apriori information about it?        (3) What if different cells are configured with different SS burst set periodicity, especially when the neighboring cells are configured with different frequency carriers?        
What is needed, therefore, and example objects of the technology disclosed herein, are methods, apparatus, and techniques to address one or more of the foregoing technical challenges.